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Saturday, February 15, 2014

#18 Dry Irish Stout - Brewday

Yeast Starter:
Lately I've just been using a single package of yeast for some of my beers since they've been somewhat small. However, the amount of yeast in a single package is usually lower than the recommended cell count for a 5 gal batch of most beers. Since I'll be using the same yeast (Wyeast 1084 Irish Ale) for this stout and the Irish red ale, I was able to make two yeast starters from the same package of yeast. I boiled the extract, 2/3 lb in 2/3 gal of water, chilled the pot in the sink, gave it a 20 second shot of pure oxygen, then added the yeast and 1/2 a tsp of yeast nutrient. This mixture got split evenly into two glass containers so I could pour the evenly split cultures into their respective batches. The yeast seemed to work quickly, finishing fermentation and flocculating in only 4 days. I gave them the rest of the week in the refrigerator to help settle out the remaining cells so I could decant the liquid off the top and only add the yeast itself to the beer on brewday.

Water Adjustments:On the last beer, I added calcium carbonate (chalk) to bump up the alkalinity, but I've been reading Water by Palmer and Kaminski, where they discourage the practice. Apparently it will not dissolve sufficiently on its own (see Kai Troester's write up for an idea of what it takes) to provide consistent results. Instead they recommend sodium bicarbonate (baking soda) which is also readily available, though it contributes sodium ions instead of calcium which I have to make up elsewhere. Calcium performs a variety of roles in the mash, boil, and fermentation to promote clarity and stability in the finished product. I will compensate with additions of calcium sulfate and calcium chloride in order to maintain the roughly 2:1 sulfate to chloride ratio of the Dublin water.

Brewday 2/15/13:
Well the first thing to go wrong was the mash tun. I had hoped to make this the first batch mashed in the rectangular cooler mash tun I bought as part of the system, but not only was I missing a couple pieces of the manifold, it doesn't even hold water. I had filled it with an OxiClean earlier in the week to get it nice and clean, but the solution ran out all over the floor of the garage.

I ended up just doing another batch using the same brew-in-a-bag (BIAB) process I've been using since I graduated to all-grain. Instead of using a separate mash tun to steep the grain, the mash happens right in the boil kettle. While it has its strengths and you can make solid beer with this method, it also has a few weaknesses vs traditional mashing methods:

Low Efficiency: Efficiency is the percentage of available sugars extracted from the grain. Without a proper sparge (rinse), BIAB tends to result require more grain to brew the same beer.

Poor Wort Clarity: Anything that can sink through the holes in the grain bag remains in the brew kettle, including proteins and small grain bits. The grain bed usually filters these out in a mash tun.

Increased Dead Space: My boil kettle has a false bottom, meaning there is nearly a gallon of wort that is not in direct contact with the grain. While this isn't a huge issue, it makes it difficult to compare the thickness of the mash (ratio of water to grain) to values in recipes and brewing literature. Mash thickness is one of the factors affecting the amylase enzymes.

Temperature Control: Unlike an insulated mash tun, the boil kettle is susceptible to wider temperature swings. This makes it difficult to hit mash temps and to reproduce exact mash conditions from batch to batch.

That last one really bit me today. The target mash temp was 150F, but I started off a hair low, and it quickly dropped to 145F. I turned on the burner to bump it back on target, but I got distracted with my new pH meter (more on this later) and after 15 minutes realized I had way overshot my temps. I cut the gas, but after the kettle finished conducting heat to the mash, the temperature was all the way up to 170F.

What did this do to the mash? Well only time will tell. And in the mean time all I can do is speculate ... so I will. I had a good 10-15 minutes in the upper 140's which is prime territory for β-amylase, so I'm thinking there should be a good amount of fermentable sugars in the wort. After that the temperature slowly rose through the 50's, kicking α-amylase into gear. The enzymes work more quickly at higher temperatures, but they can denature if the temperature gets too high: 149F for α-amylase, and 176F for β-amylase. It's tough to tell what portion of the β-amylase denatured before the mash eventually cooled back into the 150's, but based on the foaming I usually see during the hot break and the couple isolated pockets of foam here, I would guess less than half. I performed an iodine test to check for complete starch conversion, and that came out pretty clean so I proceeded with my modified sparge as normal. The final temperature profile looks similar to the German Hochkurz mash, so based on some reading there, I would guess this would be a moderately fermentable wort ... hopefully roughly where I intended in the first place, but probably a bit thicker.As I mentioned earlier, I got distracted because I was calibrating my new pH meter! Whatever I put on my Christmas list, Santa seems to deliver whether or not he knows why I want it, and this time he really delivered! It's accurate down to +/- .02 pH, unlike those test strips which are accurate to +/- is it wet? The pH at the end of the mash was about 5.4, dead center of the optimum range, so it was a relief to see something go right. All the studying I've done on water and mash chemistry, finding good water and adding specific minerals, actually worked as expected.For me, the mash is generally the most stressful part of the process: I [should] hover over the kettle, checking temperature while still trying to prepare things for the subsequent steps like cleaning and measuring hop additions. However, even after the hard work was complete things found a way to go wrong. Mother Nature came and rained on my parade. Then at the end of the boil, the hose fitting on the immersion chiller sprang a leak, so I had to stand in the rain as the beer chilled (20 min.), holding the leak closed with one hand while shielding the pot with a makeshift lid with the other. I got soaked. I don't think too much water got into the beer, so infection shouldn't be a big issue, but I would always rather have no question. And a dry shirt.Fermentation:Pure O2 for 30 sec., yeast slurry pitched from decanted starter at 65F. Carboy placed in fridge set to 63F.After only 24 hr, the yeast has already kicked things into high gear. I learned my lesson on the imperial stout a couple months ago--always use a blowoff tube--and it definitely got used here. Irish red added to fermentation fridge and temperature set to 65F.At 3 days, fermentation appears to be nearly complete. I bumped the temperature up to 68F as usual to make sure the yeast finishes and cleans everything up before going dormant.